DE19519468A1 - Slide material, esp. for pump immersion bearing - Google Patents

Abstract

A slide material consists of a porous ceramic body having open pores filled with a highly water absorbent resin, the open pore vol. of the body pref. being 5-15%. Also claimed is an immersion bearing for use in liquids and gaseous atmospheres, members of the rotating parts being made of a cemented hard alloy and members of the stationary parts being made of the above slide material.

Description

Background of the Invention

This invention relates to ceramic slip materials lines with excellent sliding properties, and not only in water, but also in gaseous form The atmosphere. In particular, the invention relates to Sliding materials that are used successfully in a wide variety of pumps, including ver tical axial flow pumps, vertical mixed flow pumps, vertical centrifugal pumps, horizontal axial flow pumps, horizontal mixed flow pumps and horizontal Centrifugal pumps, namely as construction materials of diving camps which are in a gaseous atmosphere Start the pump or stop it from running are set, but during continuous state operation or Continuous operation are submerged in water.

Materials for use in sliding contact with others Materials must have overall sliding properties that are necessary to have a satisfactory gliding effect to ensure and which is not just a self include lubrication property and wear resistance, but also the corresponding or matching one Do no harm to material, minor Have heat generation and are unbreakable. Camp that are used in power transmission systems a typical example of sliding parts that spac are intended for use under sliding conditions and therefore must have these general sliding properties sen. In particular, it is expected that diving camps in Pumps used in a variety of applications such as irrigation and drainage in agriculture and pumping rainwater and Urban wastewater, a much higher corrosion and  Have wear resistance because of the sliding surfaces used under such unfavorable conditions that these bearing fluids, occasionally corrosive fluids or slurries exposed to hard solid material.

A class of pumps that are in common use today find are vertical pumps. During vertical pumps Axial flow, mixed flow and centrifugal types include they have the common characteristic that they are a stationary res, water-conducting part and a rotating part on sen. The rotating part or the rotor begins to close turn when it is powered by a motor, which is installed near the top of the pump, and the Bearings positioned above the impeller tra radial load or load on the rotor the sleeve fitted over the latter. Some of these Bearings are located above the outer water level, during the start of the pump or at the end of its loading drifted and are not in with the surrounding water Come in contact. In other words, there are certain camps a gaseous atmosphere when starting the pump and suspended at the end of their operation (an operation under dry conditions), but during a steady state operation or continuous operation in water dives.

If the bearings used in vertical pumps are submerged in the water to be pumped, that works Water in itself as a lubricant and any solid or liquid lubricants are not required does. However, it is important to ensure that the Bearings permanently show the intended sliding effect can while exposed to a gas atmosphere during operation in dry conditions.  

Sliding materials that are traditionally used in diving camps used include rubbers (e.g. NMR or Nitrile butadiene rubber), metals (e.g. brass) and Resins (for example Teflon). Rubbers show extremely con consistent or permanent sliding properties when in Fresh water or lubricated with water or oils be used in fresh water. However, the biggest is Problem with rubbers that when they are in a gas feed atmosphere and without lubrication, generate intense heat from the sliding parts and in a short period of time so that they do not are more effective than sliding members. Therefore at Start or end the operation of the pumps, the rubber use as construction material of the diving camp, which are either in water or in a gaseous atmosphere used lubricating oils on the rubber sliding parts supplied or water is added to the rubber sliding parts injected from separately provided lubricant ver care units to protect the sliding parts that the are exposed to a gaseous atmosphere. A problem this approach is that when the pump is very is large with a shaft or wavelength that varies spanning several tens of meters, many camps used need, and the need for a lubricant to install tel supply unit for each warehouse, increased the construction or equipment costs are considerable.

Metals, such as brass, have none self-lubricating properties and are not in the Able to glide under dry conditions endure.

On the other hand, resins have good self-lubrication properties and have the advantage of being used in applications can be used that have a corrosion problem Cause metals, such as in acid or basic environments. However, resins have one  serious mistakes by using in slurry that contains hard, solid matter, wear are exposed under the abrading or grinding the effect of matter.

Ceramics are generally very hard and Compression resistance, are good electrical insulators and are resistant to electro-chemical corrosion sion. Because of these advantages, ceramics were the subject intensive studies in recent years, such as in JPA 87/27382 is taught. On the other hand, have ceramics high coefficients of friction and poor self-lubrication properties and to use them as sliding materials use, they are ge with highly viscous oils lubricated or with solid lubricants (to a com posit or composite). JPA 83/161982 proposed combining fluoropolymers with ceramics; JPA 82/118080 has suggested using porous ceramic bodies Tetrafluoroethylene or chlorotrifluoroethylene resins or Mixtures thereof with molybdenum II sulfide, tungsten II Impregnated sulfide, molybdenum selenide or tungsten selenide kidneys; and JPA 86/281086 has provided sliding materials beat, oils of fluorine compounds, such as wise fluoroethylene and fluorosilicone, in open pores of impregnated porous ceramic bodies or penetrate ge were left. However, these suggestions will be reflected in the Case does not prove to be very effective in starting a and switching off a pump is repeated cyclically because the impregnated resins or oils differ from the ceramics loosen or separate, and the initial sliding Properties of the latter can last for a long time period cannot be maintained. Therefore it is expected that bearings that have porous ceramic bodies, which with Resins or oils are impregnated while sliding under do not work satisfactorily in dry conditions.

Summary of the invention

It is therefore an object of the invention to provide bearings for Use with pumps that have such good self-lubrication possess property that they need eliminate separate lubricant supply units built in, which have been used to lubricate to deliver oil to ceramic sliding parts or water in inject ceramic sliding parts to protect them when they start a gaseous atmosphere Pump or at the end of its operation.

Another object of the invention is to provide ceramic sliding to provide materials that are consistent or lasting have strong sliding properties, and not just in Fresh water, but also in other fluids or liquids, such as sea water and River water, sand and other hard, solid matter contains, and work satisfactorily even if they are exposed to a gaseous atmosphere.

It is still another object of the invention to be ceramic To provide sliding materials that successfully as Kon construction materials of diving camps of different types of pumps that can be used for treatment not only fresh water, but also slurry or other fluids are intended, including the vertical axial flow pumps, vertical mixed flow pumps, vertical centrifugal pumps, horizontal axial flow pumps, horizontal Mixed flow pumps and horizontal centrifugal pumps.

It is still another object of the invention to be permanent Provide immersion bearings that are installed in pumps can be used to handle fluids or Liquids such as sea water and river water that contains hard, solid matter.  

The inventors of the present invention have intense Studies conducted to achieve the goals of the invention range, and have found that porous ceramic bodies per that with a highly water-absorbent resin in open pores were inherently desired Properties of the ceramic material retained, such as for example high wear and corrosion resistance, combining these properties were made with the ability of highly water-absorbent Resin to absorb and absorb large amounts of water hold, which ensures that the ceramic body show an excellent self-lubricating property would, even if they were gaseous atmospheres get abandoned.

Thus, the present invention relates to one Aspect on a ceramic sliding material, the open Pores in a porous ceramic body with a strong water-absorbent resin are filled. Preferably the volume of the open pores from about 5 to about 15%.

In another aspect, the invention relates to a dive camp for use in both liquid and also in gaseous atmospheres, that links of the rotating part of the bearing from one cemented hard alloy, whereas Links of the stationary part made of a porous ceramic body are made, the open pores with a highly water-absorbent resin are filled. Preferential wise is the volume of open pores in the porous Ceramic body between about 5 and about 15%.  

Brief description of the drawings

Fig. 1 shows schematically the structure of the sliding material of the invention;

Fig. 2 is a schematic view of a vertical axial flow pump equipped with the bearing according to the invention;

Fig. 3 is a schematic sectional view showing an enlarged side of one side of the bearing part of Fig. 2;

Fig. 4 schematically shows the slide tester used in Example 1;

Fig. 5 shows the pit formed when calculating the stress intensity factor; and

Fig. 6 is a graph or chart which shows the empirically measured relationship between the volume of the open pores in two porous ceramic bodies and their stress intensity factors.

Detailed description of the invention

The present invention will now be described in detail described.

Ceramic powders are used as starting materials in the invention material used for the porous ceramic body, and the Ceramics preferably have the highest possible hardness, to provide satisfactory wear resistance guarantee. While there are different types of ceramic ma materials there, including those based on metals based, they must have certain properties in order to to be used as sliding materials, and under These requirements are high hardness, high resistance in terms of use and seizure, sufficiently low Coefficient of friction to the associated or together only little wear on matching links, high strength and high thermal impact resistance, high thermal conductivity  ability and sufficiently small specific weights to to reduce the centrifugal load. Preferred case games of ceramic materials that meet these requirements meet, for example, silicon carbide, silicon nitride, aluminum oxide, zirconium oxide, titanium carbide, titanium nitride, boron nitride. Boron carbide and mixtures of two or more of these connections, but are not concerned limits. Further preferred examples are silicon carbide, silicon nitride, boron nitride, boron carbide and Mi created from two or more of these compounds. If the Particle size of the ceramic powder increases, the me mechanical strength of the sintered body; to the To ensure use as sliding materials therefore preferred to use ceramic powder with an average particle size of not more than 10 µm the.

The ceramic powders are made by conventional techniques molded, such as injection molding, slip molding, Ex trudging, hot rolling and HIP, and then sintered, to create ceramic bodies. Optionally, sinter aids, binders and other additives be added in reasonable amounts. The sintering can can also be performed by conventional techniques, such as reaction sintering, normal sintering and Pressure sintering. To manufacture porous ceramic bodies that have open pores into which are highly water-absorbent Resins are impregnated at a later time or should be able to penetrate, the fineness and particle size the ceramic powder and the amount of binder added in the Relationship to the ceramic powders, as well as the Sintering temperature can be adjusted or set. A Another effective method is to use ceramic powder Foams, such as urethane foams, too impregnated kidney or to let in and then the arrangement to sinter.  

If the volume of open pores in the porous kera If the body is excessively high, the sliding mat rialien by filling the pores with strong water absorbent resins are constructed, an unprak have low mechanical strength. To this To avoid problem, the volume of the open Pores in the ceramic bodies preferably about 30% do not exceed. If the volume of open pores on the other hand is less than about 5%, it will Loading or penetration of the highly water-absorbent Remove resin in the open pores, which is what the surface surface of the ceramic body that intended Lubrication can be achieved completely through the combination the water or moisture absorption capacity of the highly water-absorbent resins and their water retention ability. To avoid this problem, the Volu men of the open pores of the ceramic body preferably not less than about 5%.

If the submersible bearings in pumps, which are intended for handling slurries, such as wise river water containing hard sand from the resin impregnated sliding material according to the invention together are set or built, the volume of the open Pores in the ceramic bodies preferably in the range of about 5 to about 15%. From the data from example 2, which is described later in this description it can be seen that a high load intensity factor and therefore high toughness guaranteed is when the volume of open pores within the range mentioned.

The porous ceramic bodies thus produced are subsequently with highly water-absorbent resins filled. It is believed that strong water absorber resins have their water absorption effect through the Show interaction of two effects, one of which  Spreading of molecular chains in polymer electrolytes Reason for the rejection of carboxyl ions within the Is water and the other being the limitation sol spread through networking points. Strong water-absorbent resins, commonly known as "super Absorbent "(" super-absorbents ") refers to who who are generally able to use water in a Quantity absorbed by at least 100 times their own weight beers. Taking into account the fact that resins that rely on capillary action for an intersti tial water absorption, no more about 20 to 30 times can absorb their own weight in water easily seen that highly water-absorbent resins a surprisingly great ability to absorb water have.

Highly water-absorbent resins "breathe" also through absorbers beers of moisture in humid conditions and by releasing moisture under dry conditions gung. Another feature of the strong water absorber Resining resins are their ability to pressurize water hold back; once it's absorbed by the resins most of the water is retained, even when pressure is applied to the resins.

The highly water-absorbent resins can be based on the Starting materials are classified into strengths (graft or graft polymers and carboxymethylated starches), Celluloses (graft polymers and carboxymethyl cellulose (CMC)), synthetic polymers (polyacrylates, polyvinyl alcohols, polyacrylamides and polyethylene oxides (PEO) Etc.). While the highly water-absorbent resins typically sold as white amorphous powder products they are also available in other forms, such as for example spherical grains (pearls), granules or granules, short fibers, long fibers, non-woven Fabrics or textiles and films.  

These highly water-absorbent resins become water absorb the moment they are exposed to water become. CMC and Poval are able to between approximately Absorb 100 and about 400 g of water per gram and poly (sodium acrylate) and starch / acrylic acid systems will absorb up to 1000 g of water per gram.

Commercially available, highly water-absorbent resins include the powders of cross-linked polyacrylates, the Powder of isobutyrene / maleate system, the powder of Starch / polyacrylate system, the powder of PVA / poly acrylic acid system, hydrolyzed acrylic fibers, the powder of cross-linked PVA and the fibers of cross-linked CMC.

A variety of new uses for strong Water-absorbent resins have been used lately proposed, including applications as Sanitary products (e.g. paper diapers and Bibs), as horticultural products, such as Soil water holding devices and seed coating agents, as Building and construction materials, such as Sealants and anti-condensation agents in the Food industry as fresh food packaging materials and cold insulators, as medical Devices such as contact lenses and thrombolytic materials, and as electrical or electronic devices such as Moisture sensors and medical electrodes. However there were no reports suggesting sliding materials to combine with highly water-absorbent resins or put together.

The sliding material according to the invention is marked by filling the open pores in the porous ceramic body with highly water-absorbent resin. If the resin impregnated ceramic body as a sliding part of  Bearings used in a vertical pump exist no need to inject water before starting the pump to rotate the rotary shaft and yet absorb the resin in the ceramic body the water vapor in the surrounding humid air and holds it back to thereby a satisfactory performance or property to ensure the sliding part. When switching off the pump and another start is also no need for an additional water supply and that Water not only on the surface of the resin, but was also held inside allow the sliding part to be a constant one Performance shows.

While different types of highly water-absorbent Resins when assembling the ceramic sliding materials can be used, which are needed to a consistent or permanent performance not only in rivers liquids, but also in gases, typically one Air atmosphere to show how it is with vertical pumps If this is the case, synthetic polymers are preferred and the most preferred synthetic polymers are polyacrylates and polyethylene oxides. If these resins inserted or charged in porous ceramic bodies or be penetrated ensures their great Moisture absorption capacity that water vapor and Dew condensation in the air atmosphere effective on the Resins is adsorbed. They also have resins a pronounced ability to return water under pressure hold and therefore ceramic materials that with filled with these resins can be used successfully for designing immersion bearings in vertical pumps.

The highly water-absorbent resins, the more advantageous as an impregnating agent in porous ceramic bodies are used are particularly exemplary pass through the products made by The Nippon Synthetic  Chemical Industry Co., Ltd., under the registered Brand names "AQUARESERVE AP" are sold. you are slightly cross-linked copolymers of acrylic acid and sodium acrylate and are of different grades or classes available including AP-100 (average par particle size 300-450 µm), AP-200 (300-450 µm), AP-300 (300- 450 µm) AP-150A (200-300 µm), AP-300A (200-300 µm), AP- 100E (200-300 µm) and AP-200E (200-300 µm). Another one advantageous example is a group of products that by Sumitomo Seika Chemicals Co., Ltd. under the Registered trademark "AQUAKEEP" are sold. These are cross-linked polyacrylates and in different Degrees or classes available including 4S (average particle size 20-30 µm), 10SH-NF (20- 30 µm), 10SH-P (150-300 µm), 10SH (150-300 µm), 10SH- T (50) (300-500 µm), 10SH-T (60) (300-500 µm), 10SH-TS (50) (300-500 µm), 10SH-TS (65) (300-500 µm), EP (100-300 µm), ET (50-250 µm), SA50 (350-450 µm), SA60 (350-450 µm), SA50S (350-450 µm), SA60S (350-450 µm) and SA60N (250-350 µm), which are all white powders.

If the open pores in the porous ceramic body with highly absorbent resins will be filled preferably a large coverage by the resins or to ensure the most complete penetration possible. One of the following two methods can be used for this become:

• i) the resin particles are dispersed in a solvent giert or distributed to prepare a suspension, that are under pressure in the open pores in the ceramic body is introduced or impregnated; or
• ii) the porous Ceramic body is immersed in the resin that after Absorbing water has gelled and it becomes a Vacuum pulled to the resin in the open pores in the Allow ceramic body to penetrate or impregnate. After the impregnation step, the ceramic body is opened an elevated temperature warmed to the solvent  or remove the water by evaporation. The Im Impregnation and the warming process can either be performed once or a number of times.

The sliding material of the invention has a microscopic structure as shown in FIG. 1. It has a porous ceramic material 1 which has open pores or vacancies 2 which are filled with a highly water-absorbent resin 3 .

Because they are good electrical insulators, they have Kera miken high resistance to electro-chemical cor rosion by generating local or local Cells or contact with dissimilar materials is produced. Therefore, bearings that are ceramic Sliding material according to the invention both in the rotating use in the stationary limbs as well, one show consistent or permanent sliding properties, even if they are in corrosive fluids or Liquids are placed. For easy replacement of the bearing elements when used in pumps afford which running water handle that very contains hard, solid matter, such as sand containing river water is preferred, the stationary Ceramic sliding material members of the invention to assemble or build, whereas the rotary link which is made of a cemented hard alloy are.

Cemented hard alloys are such materials the binding metals (for example Fe, Ni, Co, Ti, Cr and Mo) own in the powder of carbides, nitrides, bori the and silicides of the elements of groups IV, V and VI of the periodic table, such as Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and Th, taken up or incorporated are. Preferred examples are those that are tungsten carbi de (WC and W₂C), preferably in amounts of approximately 40-  Contain 95 wt .-%. Preferred binders are Ni, Co and Ti.

Cemented hard alloys are generally in molds processed by sintering mixtures of the above given powder at elevated temperatures. However need not all rotating links made of cemented hard le gations and instead links can be built made of stainless steel or another metal with a Layer of cemented hard alloy coated the one that is deposited in a thickness of 1-2 mm by Powder Plasma Transfer Arc Welding (PTA) to thereby achieve the To manufacture rotating elements.

Fig. 2 is a schematic view of a vertical axial flow pump, which is permitted with the bearing of the invention. Reference numeral 1 refers to the outside water level below which an impeller or impeller 102 is located. When a drive motor 103 starts to run, its rotation is transmitted via a shaft coupling 104 , shafts 105 A and 105 B and an intermediate shaft or intermediate shaft coupling 106 in order to drive the impeller or the impeller 102 . The fluid to be pumped is drawn in through a suction cup 107 , passed through a drain bowl 108 and suspended housings 109 and 110 to be discharged through an exhaust manifold 111 . An upper immersion bearing 112 is carried by a shaft support 114 , whereas a lower immersion bearing 113 is carried by a rib 115 .

Fig. 3 is a schematic cross section showing an enlarged side of one side of the bearing part shown in Fig. 2. The shaft 105 B is combined with a sleeve 116 made of cemented hard alloy, the sleeve being fixedly attached to its periphery by means of fastening screws (not shown). The bearing 112 is secured or attached to a housing 114 by a shrink fit and is attached to the shaft support 114 . Securing or loading the bearing 112 on the housing 117 by shrink fitting offers the advantage that it is ensured that the rigidity of the ceramic body is increased sufficiently under load to protect it against failure due to deformation.

The bearing ring does not need a solid cylindrical link to be, but can consist of two or more cylindri rule segments that consist of the sliding material of the Invention exist and which are attached to the housing, as taught in JPA 85/30822. Because this construction a comparatively wide space on the la provides each side of each segment, each Foreign matter in the fluid being pumped flow axially through these gaps to thereby create a even more consistent or permanent sliding properties ensure when pumping slurries that contain hard, solid matter.

Thus, the ceramic sliding material of the invention has one Ceramic body, whose open pores with the strong filled with water-absorbent resin that dampens such as water vapor and dew condensation, absorbed when it is in an air atmosphere, or Water absorbs when immersed in water. There the moisture or water absorbed even under pressure, the glide remains surface wet or lubricated, independently whether exposed to an air atmosphere or water is.

In addition, the sliding material of the invention is the highest durable and suitable for use when pumping Slurries containing hard, solid matter there  the surface layer through the hard, solid material is not scratched.

Various examples of the invention are described with reference to the accompanying drawings. The following Examples are for illustration purposes only and should in no way limit the present Invention can be viewed.

example 1

Four different samples were prepared and measured in terms of their coefficient of friction, namely the following way.

Preparation of the samples

Samples 1 and 2 were within the scope of the invention, whereas Samples 3 and 4 were outside the scope of the invention.

Sample 1

A silicon carbide ceramic powder with an average particle size of 10 µm was obtained by extrusion shaped and sintered in an Ar atmosphere. The volume the open pores in the sintered part was 10%. The sinter part was then immersed in AQUAKEEP (polyacrylate), that gelled after absorbing water; a vacuum was pulled and heated, which caused the open pores in the sintered piece are filled with the resin were. The sample prepared in this way became like a bearing ring shaped, which has an inner diameter of 75 mm and a 40 mm wide.  

Sample 2

A silicon nitride ceramic powder with an average particle size of 10 µm was molded by extrusion and sintered in an Ar atmosphere. The volume of the open pores in the sintered piece was 10%. The sintered piece was then immersed in AQUAKEEP (polyacrylate) that had gelled after absorbing water, a vacuum was drawn, and heating was performed, thereby filling the open pores in the sintered piece with the resin. The sample thus prepared had the same shape and the same dimensions as Sample 1 .

Sample 3

A silicon carbide ceramic powder with an average particle size of 1 µm was molded by extrusion and sintered in an Ar atmosphere. The volume of the pores in the sintered piece was 0.5%, but it had no open pores. The sample thus prepared had the same shape and dimensions as sample 1 .

Sample 4

A silicon nitride ceramic powder with an average particle size of 1 µm was molded by extrusion and sintered in an Ar atmosphere. The volume of the pores in the sintered piece was 0.5%, but it had no open pores. The sample thus prepared had the same shape and dimensions as sample 1 .

Sliding tests

The bearing samples 1-4 were subjected to sliding tests to evaluate their properties in sliding contact with a shaft sleeve which was made of a cemented hard alloy consisting of 92% WC and 8% Co.

(1) Sliding test 1

The shaft sleeve was held in sliding contact with each bearing sample as shown in Fig. 4. On the shaft 121 , a SUS 304 sleeve 122 A and a sleeve 122 B made of cemented hard alloy were fixedly attached by means of (not shown) fastening screws. The bearing 123 was shrink fitted to the housing 124 and also attached to the shaft support 125 . A weight plate 126 was mounted such that an imbalance or imbalance was created to apply a radial load. A motor (not shown) was operated to rotate the shaft 121 . The shaft was rotated at three different peripheral speeds for 30 minutes at 4.0 m / sec, 6.0 m / sec and 7.5 m / sec. The test was conducted while the sliding part was only exposed to an air atmosphere (for samples 1 and 2 ) or both immersed in fresh water and exposed to an air atmosphere (for samples 3 and 4 ).

The load exerted on the bearing consists of the centri force due to the unbalanced weight of the Impeller, the centrifugal force due to a vibrating or wobbling of the rotor and the itself unbalanced hydrodynamic Power of the impeller. The two centrifugal components can be calculated, but not the third compo nente. Therefore, the axial vibration waveform significantly reduced so that they are not in the same weighted hydrodynamic force of the impeller would become negligibly small compared to the centri fugal forces, and the sum of the two centrifugal forces,  one due to the unbalanced weight of the wheel and the other due to the wobbling or swinging of the Rotor, was treated as a bearing load or load. The pressure on the bearing surface was 170 MPa at one Load at maximum frequency (maximum Hertz Burden).

After the shaft rotation ended, friction coefficients target measurements and the results are in Table 1 shown.

Table 1

When tested in the practical range of peripheral speeds (4.0-7.5 m / s), the coefficient of friction (µ) of the bearings of Samples 1 and 2 , although exposed to the air atmosphere, were reduced to levels that were comparable to those achieved when samples 3 and 4 were immersed in water. On the other hand, Samples 3 and 4 showed very high coefficients of friction when exposed to an air atmosphere. These data show that the ceramic sliding materials according to the invention work satisfactorily in an air atmosphere even if they are not supplied with a lubricant, and their lubricating property is comparable to that achieved in water.

(2) sliding test 2

Another sliding test was carried out within one Water slurry, which is a mixture of clay and Contained silt of 1: 1. The clay particles had one average size of 30 microns and the silt particles had an average size of 15 mm. The The concentration of these particles was 60 mg / l. The others Conditions of the sliding test were the same as in the test 1 except that the peripheral speed is up Was set at 5.05 m / s and the test device for 200 h was operated. The shaft was rotated at 1485 rpm and the pressure on the sliding surface was 170 MPa Load with maximum frequency or speed (maximum Hertz exposure).

The sliding surfaces of Samples 1 and 2 showed a very consistent or uniform property and performance and no part was scored or otherwise damaged by the clay or silt particles in the slurry. Therefore, it is clear that the ceramic sliding materials of the invention also have excellent toughness.

Example 2

The two groups of samples were prepared and measured with regard to their stress intensity factor in the following way.

Sample preparation Sample group 1

Silicon carbide ceramic powder with an average Particle size of 10 µm was molded by extrusion and in an Ar atmosphere under varying conditions  sintered to different values for the volume of the open pores. Own the samples prepared in this way dimensions 50 × 50 × 5 mm.

Sample group 2

Silicon nitride ceramic powder with an average Particle size of 10 µm was molded by extrusion and in an Ar atmosphere under varying conditions sintered to different values for the volume of the open pores. Own the samples prepared in this way dimensions 50 × 50 × 5 mm.

Stress intensity factor measurements

The relationship between the volume of the open pores (in%) and the stress intensity factor K _IC (in MPam ^-1/2 ) was calculated for each sample group on the basis of empirical data.

The stress intensity factor K _IC was calculated with the formula (I) or (II) depending on the profiles of the fractures or cracks. Formula (I) is:

(K _IC Φ / Ha ^1/2 ) (H / EΦ) ^0.4 = 0.129 (c / a) ^-1/2

in which:
Φ = 0.3 (constant);
H = Vickers hardness = P / 2a²;
P = load for Vickers hardness measurement:
E = modulus of elasticity = 300 GPa (for Si₃N₄) or 400 GPa (for SiC);
a = half the diagonal length of the indentation or depression;
c = half the length of the surface fracture or crack.

For a proper understanding of the relationship between a and c, see Figure 5 (I).

Formula (II) is:

(K _IC Φ / Ha ^1/2 ) (H / EΦ) ^0.4 = 0.035 (l / a) ^-1/2

in which:
Φ = 0.3 (constant);
H = Vickers hardness = P / 2a²;
P = load for Vickers hardness measurement:
E = modulus of elasticity = 300 GPa (for Si₃N₄) or 400 GPa (for SiC);
a = half the diagonal length of the indentation or depression;
l = the length of the surface break or crack.

For a correct understanding of the relationship between a and l, see Fig. 5 (II).

Fig. 6 is a graph showing the empirical relationship between the volume of the open pores and the load intensity factor for each type of ceramic. Obviously, the stress intensity factor hardly decreased before the open pore volume exceeded about 15%. It is known that the stress intensity factor correlates well with the amount of wear or the degree of wear, which decreases with the increasing stress intensity factor, as described in "Friction and Wear of Hot Pressed Silicon Nitride and Other Ceramic", Transaction of ASME, Journal of Tribology, volume 108, October 1986. Therefore, porous ceramic bodies with open pores within the volume range of about 5 to about 15% would show sliding properties which are comparable to or even better than those of solid ceramic bodies, even if the bearings made of such porous ceramic bodies were used in slurries, contain the hard solid matter. Particularly good sliding properties are achieved with silicon nitride (Si₃N₄).

Increased porosity also means increased Occurrence of cracks or breaks and therefore have in general hard and brittle or brittle materials, such as ceramics, an increased risk of Occurrence of damage when their porosity increases. In example 2, however, the volume of the open Pores set so that it is within the stated appropriate range, and it is believed that this to the essential reduction, and not one Increase, the brittle or brittle nature of the ceramic material materials has contributed.

Summary uses the ceramic sliding material of the Invention effectively the water from which highly water-absorbent resin is absorbed, so that the sliding surface is kept wet or moist by one to have lower coefficients of friction and bearings, which are formed from this sliding material become a have constant behavior when starting the pump without a supply of lubricating water. Therefore there is no need, additional water from separate pre to deliver directions or equipment.

The ceramic bearing made from the ceramic sliding material the invention is formed, can in terms of Volu mens of the open pores correctly adjusted or set so that it has wear resistance, which is at least comparable to the value that was achieved with the massive used so far Ceramic bearings.

In summary, the invention provides the following: The invention relates to sliding material, which is a porous Has ceramic body, the open pores with a  highly water-absorbent resin are filled, namely preferably with an open-pore porosity of approx. 5 to 15%. The sliding material can be used to Links of the stationary part of a rotary bearing in one Manufacture pump, for use in both a liquid as well as a gaseous one The atmosphere; Link the rotating part of the bearing made of a cemented, hard alloy. Since that Resin absorbs water and retains it Sliding material show satisfactory properties even if there is no gaseous atmosphere Lubrication is exposed. A consistent or permanent Elevated sliding property is not only guaranteed in Fresh water, but also in liquids, such as for example slurries, the hard, solid matter contain.

Claims (4)

1. Sliding material, with the open pores in one porous ceramic body with a strong water absorber resin are filled. 2. Sliding material according to claim 1, wherein the volume of open pores between about 5 and about 15% is. 3. Dive storage for use in both liquid and also in a gaseous atmosphere, with members of the rotating part from a cemented, hard Alloy are manufactured, whereas members of the sta tional part from a porous ceramic body are placed, the open pores with a strong water-absorbent resin are filled. 4. dive camp according to claim 3, wherein the volume of the open pores between about 5 and about 15% lies.